1. Field of the Invention
This invention relates to a fastening structure for fastening an article onto a wall, a panel board, or the like, via through-hole, in a detachable manner. The fastener is suitably applied to a holder for receiving a shaft of a sun visor used in an automobile, and to any other holders or retainers.
2. Description of the Related Art
In general, sun visors are furnished above the front sheets of an automobile in order to protect the driver's eyes and the passenger's eyes from the sun. The sun visor is generally attached to the upper front of the interior of the automobile to block the sunlight streaming into the car through the front glass. FIGS. 19 and 20 illustrate such sun visors furnished above the front sheets 22. The sun visor 1 has a pivoting shaft 24, which is retained by the retainer 25 fixed to the top front wall of the automobile C. The sun visor 1 swings about the pivoting shaft 24 between the home position (i.e., non-used position) and the light-blocking position (i.e., used position). The sun visor 1 also has a short shaft 26. When not in use, the sun visor 1 is rotated upward to the home position, and the short shaft 26 is received by the holder 27 so as to prevent the sun visor 1 from swinging downward.
The holder 27 is generally screwed onto the ceiling 23. However, screwing the holder 27 spoils the appearance of the interior of the car. In addition, the screw (or the vis) damages the lining and the ceiling 23. In order to overcome these problems, it was proposed to provide snappers to the holder 27. When the snappers are inserted into a through-hole, which is formed on the ceiling 23 of a car in advance, the snappers catch the edge of the through-hole, thereby securing the holder 27 onto the ceiling 23.
Japanese Patent Application Laid-open No. H4-110224 discloses such structure. In this publication, the base of the holder 27 has a projection for positioning itself, and two wavy snappers extend from the positioning projection in opposite directions. When the snappers and the projection are inserted into the through-hole formed on the ceiling 23, the two wavy snappers come into contact with the fold-back formed around the through-hole, whereby the holder 27 is attached to the ceiling 23. This structure does not spoil the appearance of the interior of a car, or damage the lining or the ceiling 23.
However, the structure disclosed in H4-110224 has some problems. The two wavy snappers are elastically deformed when they are inserted into the through-hole of the ceiling 23. After the snappers were inserted, they are spontaneously restored, and come into contact with the fold-back of the through-hole. In order to insert the snappers in the through-hole, a certain extent of force must be applied to the snappers to deform them. After the insertion, only elastic contact between the tip of the snapper and the fold-back of the through-hole supports the weight of the holder 27. This elastic contact may not be sufficient to securely support the holder 27 and the pivoting shaft of the sun visor for a long time, because the end portions of the snappers are in contact with the fold-back in the free states. Meanwhile, it is not easy to detach the holder 27 from the ceiling 23 because of difficulties to elastically deform the snappers, which are now positioned behind the ceiling, from the inside the car to pull them out of the through-hole. This inconvenience becomes conspicuous when the holder 27 needs to be repaired or changed.